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Old Dec 06, 2001, 06:18 PM
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mitc99kd's Avatar
New Zealand
Joined Nov 2001
346 Posts
To Foil or not to Foil

Hi Everyone, I have been having a debate with my Farther who is a very experienced IC pilot (27 years, from when they had push button transmitters) and he is also a registered electrian and electronic specilaist. He belives that I have rocks in my head when I wrap my reciever in foild to prevent glitching from my ducted fan aircraft.

It is his belief that altough wraping the reciever in foil will help prevent glitching he believes that it will also reduce your range and can potentially slightly alter your frequency signal.

What do you guys think??!!

Cheers


Shaun.
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Old Dec 06, 2001, 07:05 PM
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Herb's Avatar
Irvine, Calif USA
Joined Feb 1999
12,176 Posts
I believe you are right and he's wrong... It's called a Faraday cage and is discussed for ex. in any modern (post - 1850's) E&M textbook... More than that, it works ! It does exactly what you say without affecting in any way the receiver's properties (or range), whose resonant frequencies are quartz stabilized.
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Old Dec 06, 2001, 09:09 PM
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DanSavage's Avatar
Trabuco Canyon, CA
Joined Nov 2000
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Re: To Foil or not to Foil

Quote:
Originally posted by mitc99kd
It is his belief that altough wraping the reciever in foil will help prevent glitching he believes that it will also reduce your range and can potentially slightly alter your frequency signal.
Technically, he's right.

Since about 1/2" of the antenna is inside the receiver, wrapping it in aluminum foil will reduce the range. If I had to guess by how much, I would say that the range would be reduced by about 10 feet.

So, instead of being able to fly your model 5280' away, you'd only be able to fly it to 5270'.

It's my understanding that modern US (AMA-legal) radios use a narrow-band, dual-conversion super heterodyne circuit because it provides high sensitivity and good interference rejection.

I'd be curious to hear why he thinks that wrapping the receiver will alter the frequency and by how much.

Dan
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Old Dec 07, 2001, 01:49 AM
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Irvine, Calif USA
Joined Feb 1999
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Re: Re: To Foil or not to Foil

Quote:
Originally posted by DanSavage

Technically, he's right.

Since about 1/2" of the antenna is inside the receiver, wrapping it in aluminum foil will reduce the range. If I had to guess by how much, I would say that the range would be reduced by about 10 feet. [...] Dan
The shortening or lenghtening of the antenna by a fraction of a centimeter will marginally <i>enhance or reduce</i> the signal, depending on the ratio of the wavelenght to the antenna lenght (see any book on antenna theory, chapter on center fed or end-fed dipole antenna for ex). The effect is - in practical terms - here completely negligible.
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Old Dec 07, 2001, 03:16 AM
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Trabuco Canyon, CA
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Re: Re: Re: To Foil or not to Foil

Quote:
Originally posted by Herb
The shortening or lenghtening of the antenna by a fraction of a centimeter will marginally <i>enhance or reduce</i> the signal, depending on the ratio of the wavelength to the antenna length (see any book on antenna theory, chapter on center fed or end-fed dipole antenna for ex). The effect is - in practical terms - here completely negligible.
Exactly.

But to be scientifically precise, it technically would have an effect. But you'd have to be in a lab to measure the difference. Out at the flying field it doesn't mean doodly.

Dan
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